From: Iustin Pop Date: Tue, 11 Sep 2007 14:20:19 +0000 (+0200) Subject: Explain the read-balancing algorithm for RAID1 better in md.4 X-Git-Tag: mdadm-2.6.4~17 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3dacb8902913a4c025b5beb3fb334f9d8b6dc0ce;p=thirdparty%2Fmdadm.git Explain the read-balancing algorithm for RAID1 better in md.4 From: Iustin Pop There are many questions on the mailing list about the RAID1 read performance profile. This patch adds a new paragraph to the RAID1 section in md.4 that details what kind of speed-up one should expect from RAID1. Signed-off-by: Iustin Pop --- diff --git a/crc32.c b/crc32.c deleted file mode 100644 index e69de29b..00000000 diff --git a/crc32.h b/crc32.h deleted file mode 100644 index e69de29b..00000000 diff --git a/inventory b/inventory old mode 100644 new mode 100755 diff --git a/md.4 b/md.4 index cf423cbe..db39aba6 100644 --- a/md.4 +++ b/md.4 @@ -168,6 +168,13 @@ All devices in a RAID1 array should be the same size. If they are not, then only the amount of space available on the smallest device is used (any extra space on other devices is wasted). +Note that the read balancing done by the driver does not make the RAID1 +performance profile be the same as for RAID0; a single stream of +sequential input will not be accelerated (e.g. a single dd), but +multiple sequential streams or a random workload will use more than one +spindle. In theory, having an N-disk RAID1 will allow N sequential +threads to read from all disks. + .SS RAID4 A RAID4 array is like a RAID0 array with an extra device for storing diff --git a/super-ddf.c b/super-ddf.c deleted file mode 100644 index e69de29b..00000000